The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.
High volume inter-device data transfer demand increases rapidly by, for example, data center, cloud computing, high-performance computing (HPC), ultra-high definition (UHD) and three-dimensional visualization technologies. In addition, a continuous demand for optical interconnection technology for rack-to-rack, board-to-board and chip-to-chip interconnections has stepped up the optical interconnection technology to the practical stage and commercialization stage.
Following this trend, also increasing is the bandwidth of the device-to-device digital interface standards such as InfiniBand, digital visual interface (DVI), high definition multimedia interface (HDMI), DisplayPort (DP), USB 3.0, etc. Further, to increase the bandwidth of the device-to-device digital interface standards, researches are actively carried out on a small multi-channel optical module capable of transmitting a large capacity of information.
Recent smart devices increasingly demand internal optical board-to-board interconnections. Efforts are focused on installing optical modules in smart devices.
However, the optical communication technology in current commercial use is based on long distance data transmission. Most manufacturers of optical communication components and systems simply utilize the long distance optical communication technology for the short range optical communication system or the short distance optical connection with little or no modifications. This results in inefficient products of short range optical communication systems or short distance optical connection solutions from these manufacturers of optical communication components and systems.
Therefore, a cost effective optical connection solution suitable for a short range or short distance optical communication system is necessary.
One of the cost effective optical connection solutions suitable for large capacity data transfer and short distance optical connection is an optical transceiver module that uses vertical-cavity surface-emitting laser (VCSEL) and a vertical-type photodiode.
To establish an optical coupling between an optical fiber and the VCSEL or the vertical-type photodiode, it is typical to make a 90 degree change of the path of light emitted from the VCSEL or of light incident on the vertical-type photodiode. Redirecting the light needs an optical system such as a mirror or a prism, and at least one lens is necessary to enhance the optical coupling efficiency.
FIG. 1 is a conceptual diagram of an optical system included in a conventional optical transceiver.
The optical system used the conventional optical transceiver includes a transmitter collimator lens 120, a transmitter reflection prism 130, a transmitter focusing lens 140, an optical fiber 150, a receiver collimator lens 160, a receiver reflection prism 170, and a receiver focusing lens 180. Here, the optical system has an optical transmitter including the components up to the optical fiber 150 and an optical receiver including the optical fiber 150 and its downstream components.
The light generated and emitted from a light source 110 has a constant radiation angle, is emitted in a direction perpendicular to the surface of the light source 110, and is incident on the transmitter collimator lens 120. The transmitter collimator lens 120 converts light incident from the light source 110 into light beams that travel in parallel to each other. The transmitter reflection prism 130 changes the path of the light emitted from the transmitter collimator lens 120 by 90 degrees to the side where the optical fiber is. The transmitter focusing lens 140 serves to collect the light reflected by the transmitter reflection prism 130 into the optical fiber 150. The light, that is transmitted from the optical fiber 150 and emitted, is incident on the receiver collimator lens 160 which changes the incident light into light beams traveling in parallel to each other. As with the optical transmitter, the receiver reflection prism 170 changes and reflects the path of light by 90 degrees. The light reflected by the receiver reflection prism 170 is made incident on a photodiode 190 via the receiver focusing lens 180, and thereby the optical signal from the optical transmitter finally passes through the optical receiver.
The optical transmitter needs a distance equal to the focal distance between the transmitter focusing lens 140 and the optical fiber 150 for the purpose of the optical coupling between the optical system and the optical fiber. Likewise, the optical receiver needs a length of optical path for forming parallel light beams between the optical fiber 150 and the receiver collimator lens 160. Therefore, a special optical fiber alignment mechanism is indispensable for setting these distances.
With such a conventional optical system, precise measuring instruments are necessary because the light alignment process is required as described above. Additionally, in product production, optical alignment and assembly performances are sensitive to deviation between the optical system mechanism and the optical fiber mechanism, which requires a very precise management of mechanism deviations.
The conventional optical system exposes the optical fiber 150 in the air, which renders the core of the optical fiber 150 to be susceptible to contamination with fine dust and foreign substances. Depending on the severity of the contamination, the optical coupling efficiency may be fatally influenced. In addition, the exposed core of the optical fiber 150 may generate additional optical coupling loss due to Fresnel loss, which can reduce reliability.
In addition, the optical coupling efficiency in the conventional optical system depends on the quality of the cross sectional cut of the optical fiber 150, which requires special processing of the cross section of the optical fiber 150. Unless these issues are resolved, products produced using conventional optical systems are highly likely to cause malfunction or failure. Those products, that are commercialized with these internal deficiencies, are difficult to assemble by using a complete passive alignment method.
By the same token, optical alignment needs elaborate arrangements to be made within a predetermined level of error overall between the light source 110 and the transmitter collimator lens 120, the transmitter collimator lens 120 and the transmitter reflection prism 130, the transmitter reflection prism 130 and the transmitter focusing lens 140, and the transmitter focusing lens 140 and the optical fiber 150. This is also true in the case of optical reception where the light source 110 is replaced with the photodiode 190.
In other words, in order for the optical transmitter or the optical receiver to operate normally, four individual alignment factors need to be under sophisticated control. Further, time-consuming processes need to be eliminated to allow for mass production of optical assemblies.
Accordingly, a compact optical assembly is necessary which enables a sophisticated and easy alignment of an optical assembly in optical transceivers for optical communications while allowing a passive alignment of the optical assembly without requiring expensive equipment or a time-consuming process.